.a {
  position: relative;
  background: url(../../img/bg.jpg) no-repeat;
  width: 1600px;
  height: 600px;
  overflow: hidden;
}
.a .b {
  background-size: cover;
  background: url(../../img/fm.jpg) no-repeat;
  width: 1600px;
  height: 600px;
  position: absolute;
  top: 0;
  left: 0;
}
.a .b:hover {
  transform: translate(100%);
}
